1. Field of Invention
The present invention relates to an apparatus and method for analyzing the read-out signal of an optical storage media and is especially suitable for the HF signal read from the digital video disk (DVD), wherein the HF signal comprises many different signals whose periods are integer times of the system period. The present apparatus and method can be used to record the maximum and minimum values of specific period of signals for further statistical analyses.
2. Related Art
The read-out signal of the DVD disk includes a series of different signals whose periods are integer times of the system period and is also called the HF signal. The period of the shortest signal is three times of the system period T, referred to the 3T-signal, while that of the longest signal is fourteen times of the system period, referred to the 14T-signal. The statistical analyses of the maximum and minimum values of specific period of signals have become important factors for verifying the disk quality.
One conventional way for obtaining the maximum and minimum values of a signal is to use a digital storage scope for recording the signal and then analyze the recorded signal by using some special programs. But because the method mentioned above needs a great number of memories to store all the information included in the signal regardless of its being useful or not, it is only suitable for low frequency signal with a short duration of time. Therefore, due to the limited memory capacity in a digital storage scope, it is impossible to obtain enough maximum and minimum values of the 3T-signal for further statistical analyses. Consequently, such a method is not suitable for analyzing the HF signal read from the DVD disks.
The present invention discloses an apparatus and method for analyzing the read-out signal of an optical storage media, by which the high frequency (HF) signal read from the optical storage media and the eight to fourteen modulation (EFM+) signal sliced from the HF signal can be processed to obtain the DC component signal via a low-pass filter. The HF signal and the DC component signal will then be fed to a differential amplifier to obtain the AC component signal of the HF signal. The present apparatus also includes a first switch unit for choosing whether the maximum value or the minimum value will be measured. Moreover, a 3T-signal detector unit and an nT-signal detector unit will be used to detect whether the positive edge, or the negative edge, of the current EFM+ signal occurs during the time interval of detection. A second switch unit is also included to choose between the 3T-signal detector unit and the nT-signal detector unit. Finally, the period of the current EFM+ signal will be identified and the HF signal may be recorded according to the identification result for further verifications.